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With development going back until 20XX the virtio device model was first introduced for the educational "lguest" hypervisor and became the default I/O virtulaization method used with qemu/KVM and recently the default model used by
many cloud providers. The virtio devices have been partially standardized by the OASIS standardisation body in 2015 with the VIRTIO 1.0 specification which describes the transport layer and a limited set of device models.
The currently standardized device models are: network, block, console, entropy, memory ballooning and SCSI devices. Additionally to the formally standardized devices several additional devices exists as "implemented" devices such as GPU,
input, 9pfs, vsock and crypto. Some of which are currently in the process of standardization.
Virtio relies on a dma-like memory model meaning that all allocations are handled by the "driver" part of the device and the "device" implementation can directly access the allocated buffers for reading or writing. This enables a
resource a resource saving and fast operating mode. Metadata is transported using so called virt-queues that resemble ring-buffers. Depending of that architecture used, several different transport and device discovery modes are supported, PCI for
x86, mmio for ARM and channel-IO for s390. These transports are geared toward the most efficiently possible implementation per CPU architecture and allow for efficient implementations depending on the environment.
In recent years some hardware devices, like network controllers and NVMe based storage systems have evolved to be similar or compatible with the virtio protocol to allow hardware assisted I/O virtualization using para-virtualized
device models.
VIRTIO Benefits
Virtio's main benefit for the automotive industry lies in it's sheer existence and operating system support. The fact that standardized device models exists allows for multiple compatible implementations of both driver and server
parts of the system. The ubiquity of virtio in cloud and enterprise virtualization makes drivers readily available in all major operating systems which keeps driver maintenance effort to a minimum.
Due to the driver defined memory allocation model, vendors can choose to limit the resource usage and define safety properties to their own requirements without impeding the standardized model and stay interoperable with existing
device implementations.
The DMA-like nature of the devices allows for high-performant implementations that the easily compete with hardware assisted I/O virtualization models while still providing relative ease of implementation.
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To allow further success of hypervisor environments in automotive it is essential that all vendors are able to provide compelling guest runtime environments that make the usual automotive I/O devices available. The essential
devices could be defined and agreed upon by the industry.
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Vendor neutral industry bodies like GENVI and AGL can act a forum between hypervisor vendors, users and the hardware manufactures in a form that allows open collaboration in development and maintaining a standard platform
definition.
The regular events can be used as occasions for interoperability testing and standard steering. The participation in the OASIS-VIRTIO committee can be delegated to such organization to voice the automotive industries concerns and
advice in the technical committee.
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